1. Field of the Application
The present application relates to axial-flow turbine engines. More specifically, the present application relates to the inner shrouds that are connected to a row of stator vanes.
2. Description of Related Art
An inner shroud is known, which permits the primary flow of an axial-flow turbine engine to be defined by constituting an annular wall which delimits the interior of the fluid stream. Thanks to its external surface, it helps to guide the flow in the course of its expansion in a turbine, or its compression in a compressor.
In a conventional manner, an inner shroud may be mounted on the inner extremities of vanes disposed in a single annular row, which are in turn attached to an external casing. The shroud has recesses for the introduction of the extremities for the attachment of the shrouds.
The inner shroud also has the aim of ensuring a seal with the rotor around which it is positioned. For this purpose, it exhibits a layer of an abradable material interacting by abrasion with sealing lips formed on the exterior of the rotor. In operation, the sealing lips come into close contact with the abradable material, where they possibly create circular incisions, so that dynamic sealing is assured.
Document EP2075414A1 discloses a compressor for an axial-flow turbine engine comprising rectifiers equipped with segmented inner shrouds. Each inner shroud comprises a tubular wall, in which rows of apertures are provided. The latter permit the introduction of the vane feet that are used for the attachment between the shroud and the vanes. Each aperture exhibits a lip, which prolongs its contour radially, and fins join the lips of the neighbouring apertures, the assembly making it possible to add rigidity to the shroud. However, the flexural rigidity of the shroud, in particular that of its segments, remains limited. In the event of loading, most of the forces are taken up by the U-shaped branches of the shroud. In the event of vibrations, the openings are able to open further around the joints surrounding the vanes, which compromises the sealing.
Although great strides have been made in the area of axial-flow turbomachines, many shortcomings remain.